Questions tagged [udp]

User Datagram Protocol (UDP) is defined to make available a datagram mode of packet-switched computer communication in the environment of an interconnected set of computer networks. This protocol assumes that the Internet Protocol (IP) is used as the underlying protocol.

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Cannot see packets arrive on application socket that were seen by Wireshark

Using Ubuntu 14 I have a Linux machine where there are two interfaces: eth1: 172.16.20.1 ppp0: 192.168.0.2 ppp0 is connected to a device which has a PPP interface (192.168.0.1) and a WAN interface (...
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1answer
747 views

Limiting socat udp to receive one packet or timeout

When testing certain multicast connectivities in the past I have been using socat to do this: socat -u UDP4-RECVFROM:12345,add-membership=224.1.2.3:eth0,fork,reuseaddr,readbytes=32 SYSTEM:"hexdump -C"...
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523 views

Measuring latency in a GStreamer pipeline

I'm using a RTP pipeline to stream video from a camera over local network. The pipeline is: camera > h264enc > RTP > UDP > receiver_and_display How can I find out how the latency is composed?
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1answer
288 views

What are the requierements to sniff UDP packets in a Wireless Ad-Hoc network?

In a wireless Ad-Hoc network, I have two computers which communicates in UDP together from 192.168.1.3 to 192.168.1.5 I have a third computer (192.168.1.6) which wants to listen to the packets which ...
3
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1answer
45 views

What happens to data on unpolled datagram sockets?

I've tried to google this, but can't find anything. If I have a long running program that listens to a datagram (UDP) socket. If data is sent to my socket, but my program does not poll for it or read ...
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0answers
370 views

Debian ignores second multicast packet

I have a home local network with several devices. One of the devices is sending multicast packets with information about some events (smart home). It works well - I've tried to launch Multicast Tester ...
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0answers
209 views

netcat -s switch does not work or do anything at all

I have a computer with a NIC with two ports and a switch between them, and I'm trying to send data from one port to the other using netcat. I thought I could simply specify the source address (i.e. ...
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0answers
498 views

UDP Multicast not seen on PiZero with Raspbian

Looking for help troubleshooting my missing UDP Multicasts. Some background... So I finally got an Amazon Echo and was playing with fauxmo on my PiZero to see if Alexa could find my device, but she ...
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0answers
657 views

When does the kernel cut UDP datagram into MTU chunks?

I need your help/hints/remarks on an issue I'm having. Thanks Here is some context : I have two application(A1 & A2) handling PDUs with a max size of 1700bytes. Each app is on a different card(C1 ...
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0answers
424 views

Netid in ss output is confusing

I'm on an Ubuntu 14.04 x64 machine. I have something running on port 51236 and I want to know whether it's TCP or UDP. So I ran ss -an | grep 51236 and got the following output. tcp ESTAB 0 ...
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0answers
3k views

TPROXY for redirecting UDP on arbitrary ports

I want to intercept all UDP traffic leaving tap1. And possibly reply to e.g. DNS-requests. To accomplish this I wrote some python code listening to localhost and use iptables with a rule-set like this:...
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200 views

Application cannot receive UDP packet from Sony camera

I have a scenario with three devices: Android-Smartphone, Linux-Laptop (Linux mint) and a Sony a7R camera. My goal is to talk to the camera using the laptop and Sony's http-SDK via WiFi (Cam opens an ...
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0answers
600 views

Beaglebone Black not able to send raw UDP Packets with Python to laptop running Ubuntu 16.04

I created a Python 3.6 script that creates a raw UDP Packet over ethernet to a system with a known MAC Address and IPv4 Address. This script is running on a Beaglebone Black (BBB) that is connected ...
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1answer
545 views

UDP multicast client over ipv6

Simple Python UDP Server: trouble receiving packets from clients other than localhost I am trying to listen datagrams over ipv6. Here are the messages I am interrested in: $ sudo tcpdump | grep ...
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0answers
560 views

how to forward all UDP traffic to VPN client IP with ufw

I'm using sipgate with freepbx and I've got down to what I presume is the final hurdle with the one-way audio issue. From everything I've read the issue points to NAT. I need to forward all UDP ...
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0answers
874 views

UDP buffer overrun and old datagram clearing

I am reading UDP datagrams on a linux server at 700,000 per second from HDL32 LIDAR system. Interface is ipv4. Sockets are set to SOREUSADDR. I turn on the LIDAR, start up socket program, it started ...
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0answers
602 views

Emulate console by sending data on one UDP port, and receive text from another

Note: I also posted this question on SuperUser, because I'm not sure where it belongs I'm trying to establish a "console-like" connection with a National Instruments cRIO-FRC. It broadcasts its ...
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0answers
924 views

iptables rule to transfer UDP through a SSH tunnel

The problem I have two programs that runs on two distant computers and communicate through a specific protocol. All I know is that this protocol only communicates through UDP and uses the ports 1101 ...
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0answers
907 views

IPTables dropping UDP packet stream

I have a configuration where UDP packets containing encapsulated DNS data are sent to a KVM instance for processing. The KVM instance sits behind an IPtables firewall which is also doing NAT. The ...
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0answers
2k views

Linux bridge blocks UDP packet from tap interfaces

Introduction: I'm working on a 6lowPAN projects of Wireless Sensor Networks. Basically, I have a set of nodes (Contiki OS) which are running on a linux host. Each nodes have its own tap interface ...
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1answer
1k views

ICMP destination unreachable

I am working on an Arch Linux machine with an ethernet interface eth1. I have created the interface eth1:0 using ifconfig and given it a dummy hardware address (00:01:02:03:04:05). When I send a UDP ...
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0answers
25 views

Any way to block UDP for a specific applcation

Is there any way on Linux to block UDP traffic for a specific process. I tried using AppArmor deny of certain traffic, but it only supports total denial of all network access, not a specific protocol. ...
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32 views

Linux: UDP “multiplexer” inside kernel

I have an application with very high performance requirements and the following job: There is incoming UDP traffic on port 1234. The packets have as fast as possible to be sent to hosts H1, H2, ... Hn ...
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117 views

Bridge / Tunnel using netcat and named pipes

I have two devices (A and B) that should communicate with each other - indirectly via a server (S): /---\ /---\ /---\ | A | <===> | S | <===> | B | \---/ \---/ \---/...
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38 views

Receive data on a udp port and forward the same on a tcp port

I'm not sure whether this is even possible, but I want to receive some data over UDP port (say 14550) and forward it to a newly opened TCP port (say 50000). I have tried socat as of now but no success:...
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114 views

How to monitor a UDP specific port/socket?

I have an application that receives UDP packets at port 5000. In order to be 100% sure that the application is receiving all packets (for example the RX buffer could be full and some packets could be ...
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0answers
9 views

Adding UDP checksum in IP layer after Xfrm transformation

I am doing a custom transformation of the packet using xfrm tables (IPv6). As part of the transformation, I am adding a UDP header (basically putting my data into an UDP a.k.a UDP encapsulation). The ...
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19 views

Tunnelling IP Multicast traffic between two residential networks or machines

The Ableton Link music synchronization service operates by broadcasting and receiving messages via an IPv4 multicast group in the "Ad-Hoc 2" address block. In order to use the protocol to synchronize ...
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2k views

UDP send buffer error in netstat

I we are running voice application which stream UDP (RTP) packets for voice, I am investigation some strange issue where my ifconfig ens4 | grep error counter going up specifically overrun If you see ...
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0answers
541 views

Retrieving the SO_INCOMING_CPU of a UDP Socket?

The socket API provides an SO_INCOMING_CPU option, the details of which are provided in the man page: SO_INCOMING_CPU (gettable since Linux 3.19, settable since Linux 4.4) Sets or gets ...
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0answers
457 views

bridge between UDP and serial doesn't work

I've created a bridge between UDP and serial port using socat. Here is what I have socat -xv udp4:localhost:54321 open:/dev/ttyUSB1,rawer,lockfile=/tmp/s1.locak,echo=1,b115200,crnl To monitor ...
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119 views

Debian configure OpenSIPS for Websocket and UDP

I'm trying to configure OpenSIPS with OverSIP so that I could make a SIP call between a webrowser and a sip client app like Yate or Linphone. The call between two client apps (Yate/Linphone) works ...
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0answers
1k views

UDP hole punching with a third party

I am now convinced that direct "UDP hole punching" between 2 people each of them behind a NAT, without 3rd party server is really difficult / sometimes impossible (see question here and my answer ...
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1answer
643 views

Why is /proc/net/snmp not showing Udp InCSumErrors?

I'm running Oracle Linux 6.5, kernel 2.6.32-431.5.1.el6.x86_64. When I look at the Udp snmp stats it does not show me InCsumErrors. How can I see this stat? cat /proc/net/snmp | grep Udp\: Udp: ...
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105 views

write error for rmem_max on Angstrom

I am trying to tune the UDP receive and transmit buffer size. According to my real time application needs, I need to configure the Tx buffer as 6 bytes and Rx buffer as 22 bytes. I am running Angstrom ...
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0answers
343 views

Prioritize UDP over FTP, SCP, etc. in Linux

I have a setup wherein one "master" Linux system communicates with 3 "slave" systems also running Linux on a dedicated Ethernet interface(just the master & the 3 slaves). The slaves send data to ...
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1answer
801 views

How does the TCP/IP stack handle UDP packets to local host and a destination address of yourself?

I am trying to understand how the network stack (TCP/IP) handles a UDP message to localhost. I am assuming it goes down the stack and gets to the IP layer, if it sees localhost it then sends it back ...
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1answer
842 views

Using tc, I want TCP and UDP to use the same buffer

I have 2 types of traffic TCP UDP I want to apply 2 different filters on them, 1 Mbps b/w for UDP and 7 Mbps b/w for TCP But I want their traffic to use a common buffer of size 100 packets I've ...
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1answer
1k views

Detecting where to bind to receive a UDP broadcast

I'm writing an application that needs to capture and print UDP broadcasts. The network interface in use is: enp0s3: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500 inet 192.168.10....
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266 views

iptraf shows traffic on UDP/443, why?

Somehow, iptraf is telling me that I am getting traffic via port 443 in UDP instead of TCP. I checked the firewall several times, and UDP port 443 is definitely not open. I have that TCP port (...
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490 views

CentOS: Prioritize UDP traffic based on UDP port number?

We have an two important applications on a CentOS box - one is Syslog, which is using UDP port 514. The other is bind (DNS), using UDP port 53. Is there a tuning mechanism that can be used to give ...
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1answer
637 views

iptables DNAT+SNAT: unwanted multiplication of the same udp datagram (and malfunction)

trying to figure out my mistake in the following very simple scenario: |peerA|(Aip:Aport) <--> (Bdev:Bip:Bport)|NatNode|(Cdev:Cip:Cport) <--> (Dip:Dport)| peerD (peer A emits datagrams ...
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2answers
1k views

UDP Port Fowarding: channel 2: open failed: connect failed: Connection refused

My situation is as follows: I have currently trying to have a program between two Hosts send UDP packets over a SSH Tunnel. There is also a host intermediate between the two hosts. Note Server01 ...
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0answers
636 views

Why doesn't syslog traffic show up in netstat and lsof output?

I've noticed on my CentOS 5.x system that outbound syslog traffic (UDP) doesn't show up in lsof or netstat results. I've even tried stuff like watch -n .1 'netstat -l -u -n --program' to make sure ...
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881 views

Command for finding open ports

On my linux servers I have this alias set: alias ns="sudo lsof -Pi|grep -v ESTABL|grep -v CLOSED|grep -v -e '->' | tr -s ' ' '\t' | awk '{print $3 "\t" $8 "\t" $5 "\t" $9 "\t" $1}'| column -t|...
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Cannot see an EC2 VPN server from another EC2 instance

I'm using openVPN to connect to one EC2 instance from another. The client cannot see the server, however, despite that servers outside of AWS can see the server and successfully negotiate with it. ...
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0answers
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Netcat listener: Line break between syslog messages

I am playing with netcat command. On this linux system, I have set up a netcat listener on UDP 514, so that I get to see syslog messages from remote systems. $ sudo nc -v -ulp 514 listening on [::]:...
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0answers
10 views

How to measure the duration of packet from network to process

I want to measure the duration of a TCP/UDP packet from network to process. Let's say that I develop a Linux process, which provides a kind of web service. My process is listening on the port 8999 and ...
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0answers
36 views

Using nftable to duplicate udp packet

I am trying to setup udp packet duplication. Usecase will be syslog messages. These messages are beeing sent to machine A ( xxx.xxx.xxx.177 : 5140 , debian 10). They are received by a service. With ...
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2answers
29 views

Counting bytes on all connections traversing a Linux router

I have a Linux box which works as a router. How can I measure which connections send and receive how much data? For each hour, I would like something like: src_addr src_port dst_addr ...